The present invention relates generally to the cleaning of printing press apparatus and more paticularly to an automatic cleaning system for portions of the printing press apparatus.
The flexographic printing press apparatus used in the corrugated paperboard container industry is illustrative of the printing press apparatus and cleaning problems of concern herein. In such flexographic printing press sytems, an ink supply system including a pump delivers ink to an ink fountain defined by two cooperating rolls, or a single fountain roller and a doctor blade, which in turn transfers the ink to a printing plate roller which carries a printing die. The ink is pumped from a remote source or container thereof through suitable conduits to the fountain, and excess ink spilling from the edges of the fountain falls into collecting pans for return through an ink return system to the ink container. In some instances, an ink filter is disposed between the pump and the fountain, and an overflow of ink from the filter is returned to the ink source for assuring circulation of the ink within the container to inhibit the drying and/or settling of the ink therein during the printing operation.
The prior art discloses a number of automatic printing press cleaning systems such as that shown in U.S. Pat. No. 3,896,730, which includes the use of both spray nozzles for directing a water wash onto various press rolls and the delivery of wash water to the fountain while the press is being operated during the cleaning operation. In this press, the ink is pumped from a container to a gravity feed reservoir and, during washing, the wash water is collected in the container and recirculated through the use of the ink pump to the gravity feed reservoir for delivery to the fountain. The use of wash liquid sprays in a cleaning system is also disclosed in U.S. Pat. No. 3,800,702. In this instance, the sprays of wash liquid are directed onto various rolls of the press, as well as onto the inside surfaces of a gravity feed ink reservoir. The wash liquid is recirculated to the gravity feed reservoir through the use of the ink pump, and both a wash and a rinse cycle are employed. A cleaning system is disclosed in U.S. Pat. No. 3,974,768 for flexographic printing presses having a dual ink delivery and circulation system. In this patent, wash liquid is separately delivered to the fountain and the collecting pans, which normally receive spillover ink from the fountain, and no provision is made for the washing of the ink pump.
The teachings of the foregoing prior art patents may be characterized as generally providing wash liquid to the press fountain, flowing the wash liquid downstream from the fountain in a cocurrent ink flow direction using the press ink distribution system, and, in some cases, using the ink pump to recirculate wash liquid returned by the ink return system of the press in order to wash the pump and the ink supply means upstream of the fountain. A prior art cleaning system developed by the applicants herein includes delivery of wash liquid to the fountain for flow in a cocurrent ink flow direction and the delivery of wash liquid to the ink supply means in a countercurrent ink flow direction for reverse flow washing through the ink supply means and the pump.